CN1926357B - Dual ratio belt drive system - Google Patents

Abstract

A two ratio belt drive system for powering a rotating accessory. The system includes a clutch unit rotatably connected to the rotating shaft and an overrunning clutch directly mounted to the rotating shaft. The system further includes a plurality of rotating accessories rotatably connected to said clutch unit and rotatably connected to said rotating shaft by said overrunning clutch such that said accessories are driven by said clutch unit at a first speed ratio and are driven directly by said rotating shaft at a second speed ratio, with said clutch unit operating at a predetermined value of engine operating conditions, thereby creating a transition between said first and second speed ratios, with said clutch engaged upon engine start-up.

Description

Dual-ratio belt drive system

field of invention

The present invention relates to a dual ratio belt drive system for driving automotive engine accessories in a first speed ratio and in a second speed ratio. the

Background of the invention

Automotive engines generally include several accessories that are used in the operation of the engine and the vehicle. These accessories can include power steering pumps, air conditioning compressors, alternators, oil pumps, fuel pumps, and more. These attachments are generally driven by serpentine belts. A serpentine belt engages pulleys on each accessory and on the engine crankshaft. The engine crankshaft provides torque to drive the accessories. the

Because the belt is driven by the crankshaft, it must experience changes in engine speed during vehicle acceleration and deceleration. In other words, the operating speed of the accessories is directly proportional to the speed of the engine. the

Since each accessory must be designed to operate satisfactorily throughout the entire range of engine speeds, variations in engine speed, especially engine speeds greater than idle, result in inefficient operation of the accessories. This must mean that the efficiency is below optimum for a large part of the engine speed range. Additionally, at higher engine speeds, more power is required to drive the accessories, resulting in reduced fuel efficiency and reduced available torque. Therefore, it is desirable to decouple some or all of the accessories from the engine crankshaft so that they can be driven within a lower or narrower optimum speed range. the

This technology is represented by US Patent 5,700,121 (1997) to Meek Stroth, which discloses a system for powering various rotary automotive accessories. the

In order to "help" starters of small size, the prior art requires that the accessories be disconnected from the engine when the engine is started. Additionally, the prior art does not teach the use of a clutch unit in combination with a crankshaft damper for reducing engine-imposed vibrations. the

There is a need in the prior art for a dual ratio belt drive system having a clutch unit with an electromagnetic clutch that engages when the engine is started. There is a need in the art for a dual ratio belt drive system that also includes a clutch unit having a crankshaft damper. The present invention meets these needs. the

Summary of the invention

The primary object of the present invention is to provide a dual ratio belt drive system having a clutch unit with an electromagnetic clutch that is engaged when the engine is started. the

Another object of the present invention is to provide a dual ratio belt transmission system further comprising a clutch unit having a crankshaft damper. the

Further aspects of the invention will be pointed out or become apparent from the following description of the invention and the accompanying drawings. the

The present invention includes a dual ratio belt drive system for powering a rotating accessory. The system comprises a clutch unit rotatably connected to the rotating shaft and an overrunning clutch mounted directly to the rotating shaft. The system also includes a plurality of rotating accessories rotatably connected to said clutch unit and to said rotating shaft via said overrunning clutch such that said accessories are driven by said Driven by the clutch unit and directly driven by the above-mentioned rotating shaft under the second speed ratio, while the above-mentioned clutch unit is operated at a predetermined value of the operating condition of the engine, thereby forming a transition between the above-mentioned first and second speed ratios, while the above-mentioned clutch The unit is engaged when the engine is started. the

Brief introduction to the drawings

The accompanying drawings, which are incorporated in and form a part of this specification, illustrate preferred embodiments of the invention and, together with the description, serve to explain the principles of the invention. the

Figure 1 is a schematic diagram of a dual speed ratio belt drive system. the

Figure 2 is a schematic plan view of a dual-ratio belt drive system. the

Fig. 3 is a half sectional view of a clutch unit. the

Fig. 4 is a half sectional view of a dual pulley. the

Figure 4A is a half cross-sectional view of an alternative embodiment of a double pulley. the

Figure 5 is a schematic diagram of a first alternative embodiment of a dual ratio belt drive system. the

Figure 6 is a schematic plan view of a first alternative embodiment of a dual ratio belt drive system. the

Figure 7 is a schematic diagram of a second alternative embodiment of a dual ratio belt drive system. the

Figure 8 is a schematic plan view of a second alternative embodiment of the dual ratio belt drive system. the

Figure 9 is a half sectional view of a second alternative embodiment of a clutch unit of a dual ratio belt drive system. the

FIG. 9A is an alternative embodiment of the clutch unit of FIG. 9 . the

Figure 10 is a half sectional view of a dual pulley for a second alternative embodiment of a clutch unit of a dual ratio belt drive system. the

10A is a half cross-sectional view of an alternative embodiment of the double pulley of FIG. 10. FIG. the

Figure 11 is a schematic diagram of an alternative configuration including a motor generator in a dual ratio belt drive system. the

FIG. 12 is a schematic plan view of an alternative embodiment including the motor-generator of FIG. 11 . the

Detailed Description of Preferred Embodiments

Figure 1 shows a dual-ratio belt drive system. The system of the present invention operates with either a first or a second pulley ratio selected by means of the clutch unit 11 . A first pulley ratio is employed at a first engine speed. A second pulley ratio is employed at a second engine speed. the

The system consists of two belts. The belt used to transmit torque is determined by the state of the clutch unit. The first pulley ratio or the second pulley ratio is selected by engaging or disengaging the clutch unit 11 . Engage the clutch unit This state drives the system with the belt engaged with the first pulley on the clutch unit. the

In the first mode (engine speed at near idle), the second belt on the system does not transmit torque directly from the engine crankshaft, but rather transmits torque to the engine's accessories from a double pulley Also engaged with the first belt. the

In the second mode (engine speed greater than idle), the clutch is disengaged, which disengages the first pulley and the first belt from the system. The accessories are thus driven by a second belt which is engaged to the crankshaft with a one-way clutch. In the second mode, the accessories are driven at a relatively slower speed than if implemented with the first belt because the second drive pulley ratio is smaller than the first drive pulley ratio. This is because the second pulley in the second mode has a smaller diameter than the first pulley in the first mode. the

The system includes a clutch unit 11 mounted on a driver rotating shaft, such as the engine crankshaft (CRK). the

The clutch unit 11 includes first and second pulleys and a crankshaft damper, an isolator or both, and an electromagnetic clutch. The clutch unit 11 also includes a one-way clutch. the

The clutch unit 11 is connected to the engine accessories via multi-ribbed serpentine belt 16: water pump WP (pulley 17), power steering pump PS (pulley 13), alternator ALT (pulley 15), idle pulley IDL (pulley 18), and air conditioner compressor AC (pulley 19). The tensioner TEN (pulley 14) is arranged clockwise from the crankshaft behind the power steering pump double pulley 13. Belt 16 is a multi-ribbed belt known in the art. the

A second multi-ribbed belt 12 connects the clutch unit 11 with a double pulley 13 which is connected to the power steering pump PS. In this embodiment, the belt 12 is mounted on a two-point drive. As shown in FIG. 2 , belt 16 is physically disposed between the engine and belt 12 . the

The clutch unit 11 as shown in FIG. 3 includes a hub 40 and a one-way clutch 42 mounted thereon. Figure 3 shows the upper half of the sectional view, the lower half is the mirror image of said upper half and is symmetrical to the upper half. In this embodiment, hub 40 is directly coupled to the engine crankshaft (CRK). The pulley 66 includes an inner hub 44 , an outer portion 660 carrying the belt, and a damper 68 disposed between the inner hub 44 and the outer portion 660 . The inner hub 44 is engaged with the one-way clutch 42 . The damper 68 is made of an elastic material known in the art of crankshaft damper technology. Outer portion 660 has a multi-ribbed profile, but may include any profile known in the pulley art. the

The second pulley 62 is connected to the rotor 48 of the electromagnetic clutch 60 . Rotor 48 , and thus pulley 62 , is rotationally engaged with hub 40 via bearing 46 . Bearings 46 are known in the art and include ball bearings, sleeve bearings, needle bearings or any other bearing suitable for use. Coil 50 of electromagnetic clutch 60 is attached to the engine block by back plate 64 . the

Hub 40 is connected to electromagnetic clutch plate 56 via hub extension 52 and spring plate 54 . The clutch unit 11 is covered with a cover 58 which prevents dust and debris from entering the clutch unit. Clutch plate 56 engages rotor 48 based on the energized state of coil 50 . Coil 50 is connected to the engine electrical system. Because the coil 50 is contained within the width of the pulley 62, the small size of the clutch can be seen. the

Referring to FIG. 2 , the pulley 66 of the clutch unit 11 is connected to the first pulley 49 of the double-groove pulley on the power steering pump with the belt 16 . FIG. 4 is a sectional view of the double pulley 13 . Figure 4 shows the upper half of the sectional view, the lower half is the mirror image of said upper half and is symmetrical to the upper half. The double pulley 13 includes a pulley 45 and a pulley 49 , which are each connected by webs 41 . The pulley 62 of the clutch unit 11 is connected to the pulley 45 of the double pulley 13 by the belt 12 . the

The system of the present invention operates in two ways in each of the following examples. Mode 1 is for lower engine speeds (including idle). Mode 2 is used for all other operating speeds, ie above idle. the

In Mode 1, the coil 50 of the electromagnetic clutch 60 is energized so that the clutch is locked when the engine is started, allowing the accessories to be started along with the engine start. Method 1 avoids the problem of a sudden drop in engine speed if the accessories increase in speed after the engine is started due to the clutch being engaged. In mode 1, pulley 62 and hub 40 rotate together because electromagnetic plate 56 is engaged with clutch 60 , thereby rotationally locking pulley 62 to hub 40 . Electromagnetic plate 56 is directly connected to hub 40 through hub extension 52 and thus to crankshaft CRK. the

Pulley 62 transmits torque from the crankshaft via belt 12 to pulley 45, which is mounted on power steering pump PS. Fig. 4 is a sectional view of a double pulley. Pulley 49 rotates at the same speed as pulley 45 . The pulley 49 transmits torque through the belt 16 to all other accessories. the

In the mode 1, the pulley 66 is driven by the belt 16 at a rotation speed faster than the rotation speed of the pulley 62, and therefore, the one-way clutch 42 is disengaged. In mode 1, with the exception of the power steering pump, all accessories are driven in series by belts 12 and 16, but no torque is transmitted from pulley 66 to hub 40. the

For example, in the case of a 5.3L V8 engine, exemplary diameters of the pulleys in the inventive system are as follows (in mm):

Table 1

Pulley Diameter for Double Ratio Pulley System

In the system in Table 1, the crankshaft/power steering pulley ratio is as follows:

165/140＝1.17 (mode 1 [first] transmission ratio) 

128/163＝0.78 (mode 2 [second] transmission ratio) 

In Mode 1, the accessories rotate at the same speed as they do in the prior art case of a direct-connected accessory drive system. the

For comparison, exemplary prior art pulley diameters (in mm) are shown below:

Table 2

             Prior Art Pulley Diameter 

The crankshaft/power steering pulley transmission ratio in the prior art system in table 2 is as follows:

193/163=1.18

This transmission ratio is substantially the same as the mode 1 [first] transmission ratio as calculated in Table 1 above. This shows that the accessory dynamic ratio is basically the same between the systems in Tables 1 and 2. However, in the system of the present invention, the opposing accessory pulley diameters can be different, depending on weight, production cost, speed and other system requirements. the

The ratio between the crankshaft diameter in table 2 and the crankshaft pulley (66) diameter in table 1 is:

193/128＝1.5

This demonstrates that at engine speeds above idle, the overall accessory deceleration provided by the inventive system outperforms the prior art system. the

The pulley 62 may have a diameter of 193mm instead of the 165mm of the prior art system. Since the diameter of the pulley 45 is smaller, ie 140 mm instead of 163 mm, the diameter of the pulley 62 can be reduced to 165 mm in the inventive system. In mode 1, the transmission ratio between the crankshaft and the power steering pump remains the same:

193/163=165/140=1.17. the

In mode 2, the electromagnetic clutch 60 is disengaged and the clutch 42 is engaged. During the transition from mode 1 to mode 2, the clutch can be disengaged for a period of time, such as 3 seconds, in order to reduce the impact on the belt and system. The coil 50 is electrically connected to an energy source such as a car battery or an alternator, and is controlled by an engine CPU (Central Processing Unit). CPU includes computer, memory, connecting bus and connecting wires. The CPU detects predetermined engine operating conditions, and the CPU calculates a predetermined value for engaging or disengaging the clutch unit based on at least one of a plurality of detected operating conditions including accessory load, engine speed, battery charge , throttle valve position, engine coolant temperature, vehicle gear selection, vehicle speed, absolute manifold pressure, ambient air temperature, intake mass flow rate and accelerator position. As selected operating conditions change through engine acceleration or deceleration, the clutch is energized or de-energized accordingly. the

In mode 2, the second pulley 62 rotates freely on the ball bearing 46 together with the rotor 48 , so there is no torque transmission between the pulley 45 and the pulley 62 . No torque is transmitted by belt 12 between pulley 45 and pulley 62 . The accessories are only driven by the belt 16 because the clutch 42 is disengaged. Clutch 42 drives pulley 66 through hub 40 . The engine transmits torque to the accessories through pulley 66 . the

In the case of rapid engine deceleration, when the accessories due to their inertia can transmit torque towards the engine, clutch 42 is disengaged, allowing the accessories to slow down at a rate lower than the engine deceleration rate. This reduces wear on the belt 16 . the

The diameter of the pulley 66 is relatively small compared to the diameter of the pulley 62 . For example, pulley 66 has a diameter of 128 mm instead of 165 mm. This reduced pulley ratio reduces the relative speed of all driven accessories to 1/1.5. the

The first embodiment described here requires minimal axial space for the belt drive system, however, the clutch unit 11 does require a certain amount of additional axial space for the electromagnetic clutch 50 as well. This space amounts to about 20-25mm. the

Figure 4A is a cross-sectional view of an alternative embodiment of a double pulley. Figure 4A shows the upper half of the cross-sectional view, the lower half is the mirror image of and is symmetrical to the upper half. In this embodiment, the elastic member 226 is disposed between the web 41 and the pulley 45 . The double pulley 13 is connected to an accessory, in this case the power steering pump P_S. The elastic member 226 acts as a vibration isolator to reduce the magnitude of engine vibrations that would otherwise be transmitted through the belt 12 from the crankshaft to the accessories. The isolator is primarily effective at engine idle speed, since at speeds above idle the clutch unit 11 disconnects the pulley 45 from the crankshaft so that it does not receive torque. The elastic member may comprise any natural or synthetic rubber or combination of natural and synthetic rubber known in the art. the

Figures 5 and 6 show a first alternative embodiment where the clutch unit 11 transmission comprises a double pulley assembly 29 which is connected to the air conditioner compressor. the

In this case, the diameter of each pulley is as follows:

table 3

Pulley Diameter for Double Ratio Pulley System

The crankshaft/A_C pulley transmission ratio in the system in Table 3 is as follows:

193/112＝1.72 (mode 1 [first] transmission ratio) 

128/112＝1.14 (mode 2 [second] transmission ratio) 

The operation of the system is the same as described for the embodiment of FIGS. 1 and 2 . The advantage of installing a double pulley on the A/C compressor is to utilize the available space, since the electromagnetic clutch is usually integrated into the A/C compressor pulley. the

One operation-related thing is belt replacement. However, belt 16 may need to be replaced more often considering that belt 12 is used 5-10% of the time and belt 16 is used all the time, being the innermost belt with respect to the engine. In the disclosed embodiment, both belts 12 and 16 must be removed even though only one of the belts may need to be replaced. the

In order to solve these problems, another embodiment is also described. the

Figures 7 and 8 show a second alternative embodiment. The two-point drive belt 32 is located closer to the engine than the serpentine belt 36 . Belt 36 is positioned outwardly from belt 32 away from the engine. the

Even though the concept and function of all elements of this embodiment are similar to those of the above-described embodiments, the design and placement of the various parts are slightly different. The main difference in this second alternative embodiment is that the electromagnetic clutch unit 33 is mounted on the power steering unit P_S, see Fig. 9, instead of on the crankshaft. In this embodiment, a double pulley unit 31 is mounted to the crankshaft, see FIG. 10 . the

Referring again to FIG. 9 , the clutch unit 33 includes an electromagnetic clutch with a coil 57 . Figure 9 shows the upper half of the cross-sectional view, the lower half is a mirror image and symmetrical to the upper half. The coil 57 is connected to a fixed housing 77 through a back plate 75 . Housing 77 does not rotate and is used to mount the clutch to a surface, such as an engine surface. A rotor 73 with a pulley 71 is rotatably mounted on a ball bearing 55 on a housing 77 . Bearing 55 comprises a ball bearing, but may comprise any suitable bearing known in the art. The clutch plate 61 is articulated to a second pulley 69 with several shafts 67 , for example three shafts 67 , spaced symmetrically around the pulley 69 . Rubber pad 65 biases clutch plate 61 away from rotor 73 when coil 57 is de-energized. This connection allows clutch plate 61 to move axially from pulley 69 towards rotor 73 when coil 57 is energized and thus the clutch is engaged. The pulley 69 also includes a hub 53 by which the pulley 69 is directly connected to an accessory, such as a power steering pump shaft. It can be seen that since the coil 57 is contained within the width of the pulley 71 and the clutch plate 61 is contained within the width of the pulley 69, the clutch obtains a small size. the

Referring again to FIG. 8, in this second alternative embodiment, in Mode 1 the electromagnetic clutch 57 is engaged. Clutch plate 61 has a frictional engagement with rotor 73, thereby causing pulleys 71 and 69 to rotate in unison. Pulley 90 , rigidly connected to the crankshaft, transmits torque to pulley 71 . Belt 32 is under load. Pulley 69 transmits torque to all accessories, including pulley 86 , however, one-way clutch 82 is disengaged so that no torque is transmitted from pulley 86 to hub 80 . In this manner, the one-way clutch 82 is disengaged. All torque is transmitted from the pulley 90 through the belt 32 . the

In Mode 2, when the coil 57 is not energized, the pulley 71 spins freely and transmits no torque because the belt 32 is disconnected from the system. Clutch 82 is engaged and transmits torque to the accessories. Pulley 69 transmits torque as it is connected to hub 53 which is directly connected to the accessory shaft. the

The diameters of all the above pulleys are as follows (in mm):

Table 4

Pulley Diameter for Double Ratio Pulley System

The transmission ratio of the crankshaft/power steering pulley in the system in Table 4 is as follows:

165/140＝1.18 (mode 1 [first] transmission ratio) 

128/163＝0.78 (mode 2 [second] transmission ratio) 

The diameter of the first pulley 86 is determined in the same manner as in the first embodiment described above. In this way all accessories are about 1.5 times slower than direct coupled prior art systems. the

In this embodiment, the axial space required by the electromagnetic clutch 33 is arranged between the power steering pump and its double pulley assembly. To accommodate this extra length, it may be necessary to move the power steering pump along the engine longitudinal axis towards the engine flywheel. the

All components in all disclosed embodiments are components known in the art. For example, one-way clutches are available from Formsprog. Electromagnetic clutches are available from Ogura. For example, Figures 3 and 9 show a standard clutch, model number 6557162, with a maximum torque of 128 N-m (Figure 3) and model number 10515376, with a maximum torque of 120 N-m. the

FIG. 9A is an alternative embodiment of the clutch unit of FIG. 9 . Figure 9A shows the upper half of the cross-sectional view, the lower half is the mirror image of the upper half and is symmetrical to the upper half. In this embodiment, the elastic member 246 is disposed between the pulley 71 and the rotor 73 . The elastic member 246 comprises a damper when the clutch unit 33 is directly connected to the crankshaft. In this embodiment, the elastic member 246 comprises a vibration isolator when the clutch unit 33 is directly connected to the accessory shaft, as shown in FIG. 8 . The elastic member 246 may comprise all natural or synthetic rubbers known in the art, or combinations of natural and synthetic rubbers. the

Figure 10 is a cross-sectional view of a dual pulley of a second alternative embodiment of a clutch unit for a dual ratio belt drive system. Figure 10 shows the upper half of the cross-sectional view, the lower half is the mirror image of and symmetrical to the upper half. A double pulley 31 is shown in the system of FIG. 8 . Pulley 90 is connected to hub 80 . Pulley 86 is rotationally engaged to hub 80 via one-way clutch 82 . The elastic damper 330 is disposed between the pulley 86 and the rotor 84 . The damper 330 attenuates torsional vibration of the crankshaft. The elastic damper may comprise all natural or synthetic rubbers known in the art, or combinations of natural and synthetic rubbers. The rotor 84 is engaged with the one-way clutch 82 . The pulley 86 also includes an inertia member 88 that helps reduce speed and torsional transients caused by engine firing. It also utilizes the inertia of the accessories when the clutch 82 is overloaded. Inertia member 88 comprises a block sized according to the vibration and inertia characteristics of the engine crankshaft and the damping requirements of the system. the

FIG. 10A is a cross-sectional view of an alternative embodiment of the double pulley of FIG. 10. FIG. Figure 10A shows the upper half of the cross-sectional view, the lower half is the mirror image of the upper half and is symmetrical to the upper half. In such an embodiment, a resilient damper 302 is disposed between the pulley 90 and the hub 80 . In this embodiment, a double pulley 31 is connected to the engine crankshaft. The damper 302 acts as a damper to isolate crankshaft vibrations that would otherwise be transmitted through the belt 16 to the accessories. The effect of the damper 302 is greatest at speeds above engine idle, where the damper absorbs inertial loads but not torque loads, since clutch 60 is disengaged at engine speeds above idle. The elastic member may comprise any natural or synthetic rubber, or a combination of natural and synthetic rubber, all known in the art. the

In any of the embodiments described above, either or both belts 12 or 16 may comprise low modulus belts as are known in the art. Low modulus belts include belts having tensile cords comprising nylon 4,6 or nylon 6,6 or a combination of both. The modulus of elasticity of the belt is in the range of about 1500 N/mm to about 3000 N/mm. The low modulus belt is characterized in that it can be installed on a belt drive system without tensioner or live shaft attachments. The low modulus belt is simply installed with belt installation tools known in the art. The installation tool described above can be used to roll or push the belt sideways over the edge of the delivery or accessory pulley without otherwise adjusting the center position of the pulley shaft. Low modulus belts are especially suitable for two-point belts, namely belt 12 and belt 32, because designing the drive in a removable manner so that the belt 12 and belt 32 can be installed and adjusted is less effective than designing the drive in a direct connection It is more expensive to attach to an engine mounting surface such as an engine block. Additionally, adjusting the propshaft position relative to the crankshaft also consumes more assembly time. the

In an alternative embodiment, the system of the present invention includes a combination of a motor generator and accessories. Figure 11 is a schematic diagram of an alternative embodiment including a motor generator. The motor generator M/G is engaged with the belt 16 via a pulley 150 which is engaged with the belt 16 . Since motor generator M/G includes a generator, the alternator included in the embodiment shown in FIG. 1 is omitted. Additionally, a tensioner Ten (pulley 20) is included in this alternative embodiment to ensure proper belt tension. Tensioners TEN are known in the art. The system shown in FIG. 11 is as described in FIG. 1 except as described in FIG. 12 . the

Figure 12 is a schematic plan view of an alternative embodiment including a motor generator. Alternative systems work in two ways. the

Initially, in the first mode, motor generator M/G operates as an electric motor when the engine is turned off. The M/G runs accessories such as the power steering pump (P_S) and air conditioning compressor (A_C) while the engine is off and works as an electric motor. In this mode, the M/G is used to start the engine on demand. After starting the engine, the M/G acts as a generator in a second way for powering the vehicle accessories and for charging the battery 800 to provide electrical energy. the

When the engine is started from a standstill, the M/G in motor mode turns the engine crank. Clutch 60 is engaged, thereby engaging belt 12 and pulley 62, thereby transferring torque from M/G through belt 16 to pulley 13, to belt 12, to pulley 62, and thus to the crankshaft. the

During the engine starting process, the controller 500 detects the speed of the M/G. The controller 500 causes the converter 400 to perform switching operations in order to achieve the torque and speed required to start the engine. For example, if the signal for switching on and off the air conditioner A/C is on when the engine is started, a higher torque is required compared to the off state of the A/C. Therefore, the controller 500 applies switching control signals to the converter 400 to allow the M/G to rotate at a higher speed with a higher torque. the

The switching control signal may be determined by various state signals of the engine and the vehicle, which are provided to the controller 500 and thus compared with a characteristic map memory stored in a memory. Alternatively, the switching control signal may be determined by calculation performed by a central processing unit (CPU) provided in the controller 500 . the

Once the engine is running, the M/G operates as a generator and implements the dual ratio pulley operation described elsewhere in this specification. That is, clutch 60 is engaged for a first operating speed range of engine state and near idle, and clutch 60 is closed or disengaged for a second operating speed greater than idle, as described herein. The accessories are connected to the clutch unit and the one-way clutch so that when the engine is running, the accessories are driven by the clutch unit at a first speed ratio and by the one-way clutch at a second speed ratio, the first and second The speed ratio is selected by engine operating conditions. the

Using M/G in the system enables dual fuel economy improvements. In the first case, fuel economy improvements are achieved by operating the accessories at reduced speed ratios for speeds above idle. In the second case, fuel economy improvements are achieved by allowing the motor-generator to operate while the engine is stopped at predetermined vehicle operating conditions, such as at red lights. the

More specifically, clutch 60 is engaged as described in FIG. 1 when using the M/G as a generator and operating the engine near idle speed. At engine speeds above idle, clutch 60 is closed and one-way clutch 42 is engaged, thereby transferring torque from the crankshaft through pulley 66 and through belt 16 to the accessories. the

Clutch 60 is disengaged when the accessories are operated by the motoring M/G and the engine and crankshaft are stopped. Because clutch 60 is open, in effect, this configuration acts as if clutch unit 11 were in "neutral" gear, thus preventing torque from being transmitted from pulley 150 and belt 12 to the crankshaft. Also, in this manner, the one-way clutch 42 is in overrunning mode, so no torque is transmitted from the belt 16 to the crankshaft. Therefore, the accessories are driven by the M/G without turning the crankshaft. In this case, controller 500 applies switching control signals to converter 400 to rotate the M/G at a speed and torque corresponding to the load of the desired accessory. Of course, for engine speeds greater than idle, clutch 60 is also disengaged, as described in FIGS. 1 and 2 . the

When an engine stop signal is received, the controller 500 stops the engine by transmitting a signal for interrupting fuel supply to the engine, for example, to an electric fuel pump (not shown). The engine stop operation may be performed under conditions such as zero vehicle speed, partial or full braking, and a gear lever in a D or N setting. The signal to stop the engine is used to disengage clutch 60, thereby disengaging belt 12 from the crankshaft. the

The above description is not intended to limit the application of the system of the present invention. In each of the above-described embodiments, the diameter of each pulley in the system can be selected to provide the desired transmission ratio. the

While various forms of the invention have been described herein, it will be apparent to those skilled in the art that changes may be made in the construction and relationship of parts without departing from the spirit and scope of the invention described herein. Various changes. the

Claims (14)

1. A double speed ratio belt drive system, comprising: a clutch unit mounted directly to the rotating shaft of the drive; a one-way clutch mounted directly to the rotating shaft of the drive; a plurality of rotating accessories, said accessories being rotatably connected to said clutch unit and to said drive means rotating shaft via said one-way clutch such that all of said accessories are driven by said clutch unit in a first speed ratio , while the rotating shaft of said driving means is directly driven at a second speed ratio through said one-way clutch, said clutch unit operates at a predetermined value of engine operating conditions, thereby defining transitions between said first and second speed ratios, wherein the above-mentioned first speed ratio is greater than the second speed ratio; a controller for operating the above-mentioned clutch unit at the above-mentioned predetermined value; and The aforementioned clutch unit is engaged when the engine is started. 2. The system of claim 1, wherein said clutch unit comprises an electromagnetic clutch. 3. The system of claim 1, wherein said controller receives input from a plurality of sensors. 4. The system of claim 3, wherein said controller calculates said predetermined value based on at least one of a plurality of detected operating conditions including accessory load, engine speed, battery charge, throttling Valve position, engine coolant temperature, vehicle gear selection, vehicle speed, intake manifold absolute pressure, ambient air temperature, intake mass flow rate or accelerator position or a combination of 2 or more of the above. 5. The system as claimed in claim 4, wherein said controller causes said clutch unit to start disengaging at said predetermined value until the clutch unit is completely disengaged, thereby defining a disengagement period, said disengagement period for about 3 seconds. 6. The system as claimed in claim 4, wherein said controller causes said clutch unit to engage at said predetermined value after the engine is started, until said clutch unit is fully engaged, thereby limiting the engagement time period, while said engagement time The segment is about 3 seconds. 7. Double speed ratio belt drive system, including: engine; electric generator; accessories having an accessory shaft driven by a motor-generator or by an engine; a clutch unit operatively disposed between the motor-generator and the engine, engagement of the clutch unit causes the motor-generator to start the engine; a one-way clutch operably disposed between the engine and the motor-generator, engagement of the one-way clutch causes the engine to drive the motor-generator; a controller, the controller is used to make the above-mentioned clutch unit operate at a predetermined value of the operating condition of the engine; The accessory is connected to the clutch unit and the one-way clutch so that when the engine is running, the accessory is driven by the clutch unit at a first speed ratio and by the one-way clutch at a second speed ratio, the first speed ratio and the second The speed ratio is selected by the engine operating conditions; and The clutch unit is disengaged for operation of the second speed ratio. 8. The system of claim 7, wherein the clutch unit further comprises an electromagnetic clutch. 9. The system of claim 7, wherein the clutch unit is disposed on the engine crankshaft. 10. The system of claim 7, wherein the clutch unit is disposed on the accessory shaft. 11. The system of claim 7, further comprising a dual pulley disposed on the accessory shaft. 12. The system of claim 7, further comprising a vibration dampening member disposed between the accessory and the engine. 13. The system of claim 9, further comprising a vibration dampening member disposed between the one-way clutch and the accessory. 14. The system of claim 9, further comprising a vibration dampening member disposed between the one-way clutch and the motor-generator.

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